An imaginary-{gamma}{sub t} lattice with dispersion-free straights for the 50 GeV high-intensity proton synchrotron

During polarized beam experiments, the 50 GeV proton synchrotron, proposed by the Institute of Nuclear Study of Japan, requires zero-dispersion straight sections. This will be implemented by turning on a special excitation of the quadrupoles resulting in a dispersion wave through the arcs of the machine. Aside from the inconvenience of the power supply, this special excitation also brings about unwanted high betatron functions and high dispersion functions, which will eventually limit the performance of the accelerator at high intensities. In this paper, dispersion suppressors are introduced. A new preliminary lattice that contains two straight sections with nonzero dispersion and two straight sections with zero dispersion is presented. The whole ring remains having a reasonable imaginary {gamma}{sub t}. The horizontal and vertical betatron functions have been kept to below 32.4 m and dispersion function between -0.52 and 1.86 m. The number of 6.2 m dipoles is reduced from 96 to 92, and the dipole field at 50 GeV will become slightly above 18 T. Some analysis of the new lattice is discussed. 10 refs., 9 figs., 1 tab